Preliminary assessment of the use of an amorphous silica residual as a supplementary cementing material

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An amorphous silica (AS) by-product was investigated as a possible supplementary cementing materials (SCM). Standard ASTM tests for the SCM as well as specific surface area measurement, electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Si nuclear magnetic resonance (NMR) spectroscopy, thermal analysis, and cement paste and mortar cube strength studies were conducted. A 10:90 AS:OPC paste (w/cm of 0.4) and mortar cubes (w/cm = 0.50 to 0.60) were prepared. AS is a white amorphous materials (x̄ = 29 ± 9 (1 σ) nm) with a surface area of 95,000 m /kg, the latter resulting in a high water demand. All of the AS in 10:90 AS:OPC paste reacted by 7 days, consuming more than 50% of the calcium hydroxide. The compressive strength of OPC paste remained unchanged with the addition of AS but that of mortar increased. 29 2

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Cement and Concrete Research

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